1. Field of the Invention
The present invention relates to a denuder for removing gases from an aerosol stream to measure their concentrations separately.
2. Description of the Related Art
An annular denuder system (ADS) uses a cyclone to remove particles greater than a certain diameter, at least one coated annular denuder tube to collect gases, and a filter which traps and collects particles. The coating on the inside surface of the annulus is a specially prepared resin absorbent for vapor absorption. A honey-comb denuder system (HDS) uses an impactor to remove particles having diameters greater than 2.5 μm from an inlet, and gases are collected by the two honey-combs coated with different chemical materials after the inlet.
The ADS and HDS can't classify particles of different diameters for further weighing and chemical analysis. The collection capacity of particles is limited since the substrates of the impaction plate of the HDS is made of flat plate and particle deposit on the plate can be reentrained easily. In addition, particles collected in the cyclone of the ADS are hard to retrieve for further weighing and chemical analysis. Furthermore, most prior art denuders can only be used for atmospheric sampling, and is not good for industrial environments with high pollutant concentrations.
Therefore, it is desirable to provide a porous metal denuder that is able to classify particles of different sizes, has high collection capacity for particles at impactor stages which use porous material as substrates, to use coated porous discs to collect gases of high concentration.